This invention relates to a security document, in particular bank note, identity card or the like, having a security element provided at least partly with a magnetic material, as well as to a method for producing the security document.
Security documents with magnetic materials disposed on or in the document have been known for some time. The magnetic materials can be for example applied in the form of stripes or disposed on separate carrier materials which are in turn firmly connected with the document.
Such a security document is known for example from DE-PS 16 96 245. This print discloses a method wherein a suitable carrier material such as silk, cotton or plastic is provided with a magnetic coating mixture and subsequently embedded in a security document. The security document can be clearly identified mechanically by the incorporated security element, in particular an incorporated security thread.
DE 41 01 301 furthermore discloses a security document having an incorporated magnetic security element wherein the magnetic coating has soft-magnetic pigments. These light gray to silver pigments are admixed to a suitable varnish and spread with it onto a carrier material and subsequently embedded in the security document so that the incorporated magnetic security element hardly appears by reflected light.
Security documents having magnetic security elements can be tested for instance, as described in DE 27 54 267 C3, by measuring the coercivity of the element.
Up to now one has mostly used commercial iron oxides in security documents as are also applied in audiotape and video technology. These are usually Fe.sub.3 O.sub.4 with a coercivity in the range of from approx. 350 to 1000 Oe, this medium coercivity guaranteeing relatively simple magnetizability and simultaneously sufficient permanent magnetization. Forgeries of security documents which simulate the impression of an authentic security thread using commercial audiotapes are therefore not excluded.
The problem of the present invention is thus to propose a security document and method for producing it which has a magnetic material whose magnetic properties are designed so that they are difficult to imitate.